1. Field of the Invention
The present invention relates to a packed battery used as a power source for portable appliances such as cameras or a backup power supply for memories in electronic apparatus. It also relates to a method of making such packed battery.
2. Description of the Prior Art
Packed batteries of the type described are known as disclosed, for example, in Japanese Utility Model Laid open Publication Nos. 60-16045 and 61-39861. The disclosed packed batteries comprise a split case formed of synthetic resin, and a power generating element composed of a plurality of cylindrical cells connected in series and disposed within an interior space defined by two halves of the split case. Positive and negative terminals are exposed to an upper surface of the split case for permitting the electric current to be drawn from the packed battery.
In the manufacture of the known packed batteries, as shown in FIG. 7 of the accompanying drawings, it has been customary practice to first place in one case member C of a split case having a pair of cutout recesses A, B of the same width as positive and negative terminals G1, G2, a power generating element composed of a plurality of cells E, F connected in series by a conductive connector D or a conductor having a positive temperature coefficient (PTC) layer or device which has previously been welded to the bottom ends of the respective cells. Then, the positive and negative terminals G1, G2 of about 4 mm thick are set in retainer recesses H2, H1 of the case member C and electrically connected by resistance welding to the top terminal end faces of the respective cells F, E. Finally, the other case member I is assembled with the case member C to fully encase the power generating element and the two case members C, I are bonded together to complete a packed battery.
In recent years, the appliances employing the packed batteries have found a wide variety of applications which then have brought about an increasing desire for a packed battery capable of meeting requirements including a large capacity, a large welding strength against shock or impact forces tending to detach the terminals, and a simple welding of the terminals to the top terminal end faces of the respective cells to improve the productivity. The conventional packed batteries of the foregoing construction and the method of making the same are however not satisfactory for the reasons described below. Since cutout recesses A, B in the case C have the same width as the terminals G1, G2, there is provided only a small space available for receiving an electrode head of a welder when the terminals G1, G2 are welded to the cells E, F. This small space needs a specifically designed welder head and a complicated setting of the welding positions of an automated packed battery 4 machine. Furthermore, the individual cells E, F are completely received in the split case, so that the capacity per unit volume of the battery is necessarily reduced to a certain extent depending on the thickness of the split case. With this fully encased construction, the conventional packed batteries fail to meet the desire for a large capacity packed battery.